A versatile toolkit to produce sensitive FRET biosensors to visualize signaling in time and space

Genetically encoded, ratiometric biosensors based on fluorescence resonance energy transfer (FRET) are powerful tools to study the spatiotemporal dynamics of cell signaling. However, many biosensors lack sensitivity. We present a biosensor library that contains circularly permutated mutants for both the donor and acceptor fluorophores, which alter the orientation of the dipoles and thus better accommodate structural constraints imposed by different signaling molecules while maintaining FRET efficiency. Our strategy improved the brightness and dynamic range of preexisting RhoA and extracellular signal-regulated protein kinase (ERK) biosensors. Using the improved RhoA biosensor, we found micrometer-sized zones of RhoA activity at the tip of F-actin bundles in growth cone filopodia during neurite extension, whereas RhoA was globally activated throughout collapsing growth cones. RhoA was also activated in filopodia and protruding membranes at the leading edge of motile fibroblasts. Using the improved ERK biosensor, we simultaneously measured ERK activation dynamics in multiple cells using low-magnification microscopy and performed in vivo FRET imaging in zebrafish. Thus, we provide a construction toolkit consisting of a vector set, which enables facile generation of sensitive biosensors.

Combined lysophosphatidic acid/platelet-derived growth factor signaling triggers glioma cell migration in a tenascin-C microenvironment

The antiadhesive extracellular matrix molecule tenascin-C abrogates cell spreading on fibronectin through competitive inhibition of syndecan-4, thereby preventing focal adhesion kinase (FAK) activation and triggering enhanced proteolytic degradation of both RhoA and tropomyosin 1 (TM1). Here, we show that simultaneous signaling by lysophosphatidic acid (LPA) and platelet-derived growth factor (PDGF) initiates glioma cell spreading and migration through syndecan-4-independent activation of paxillin and FAK and by stabilizing expression of RhoA, TM1, TM2, and TM3. By using gene silencing methods, we show that paxillin, TM1, TM2, and TM3 are essential for LPA/PDGF-induced cell spreading on a fibronectin/tenascin-C (FN/TN) substratum. LPA/PDGF-induced cell spreading and migration on FN/TN depends on phosphatidylinositol 3-kinase, RhoKinase, and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 but is independent of phospholipase C and Jun kinase. RNA microarray data reveal expression of tenascin-C, PDGFs, LPA, and the respective receptors in several types of cancer, suggesting that the TN/LPA/PDGF axis exists in malignant tumors. These findings may in turn be relevant for diagnostic or therapeutic applications targeting cancer.

Endothelin receptor type B counteracts tenascin-C-induced endothelin receptor type A-dependent focal adhesion and actin stress fiber disorganization

Tenascin-C, an extracellular matrix molecule of the tumor-specific microenvironment, counteracts the tumor cell proliferation-suppressing effect of fibronectin by blocking the integrin alpha(5)beta(1)/syndecan-4 complex. This causes cell rounding and stimulates tumor cell proliferation. Tenascin-C also stimulates endothelin receptor type A (EDNRA) expression. Here, we investigated whether signaling through endothelin receptors affects tenascin-C-induced cell rounding. We observed that endothelin receptor type B (EDNRB) activation inhibited cell rounding by tenascin-C and induced spreading by restoring expression and function of focal adhesion kinase (FAK), paxillin, RhoA, and tropomyosin-1 (TM1) via activation of epidermal growth factor receptor, phospholipase C, c-Jun NH(2)-terminal kinase, and the phosphatidylinositol 3-kinase pathway. In contrast to EDNRB, signaling through EDNRA induced cell rounding, which correlated with FAK inhibition and TM1 and RhoA protein destabilization in the presence of tenascin-C. This occurred in a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-dependent manner. Thus, tumorigenesis might be enhanced by tenascin-C involving EDNRA signaling. Inhibition of tenascin-C in combination with blocking both endothelin receptors could present a strategy for sensitization of cancer and endothelial cells toward anoikis.

Growth promoting signaling by tenascin-C [corrected]

Tenascin-C is an adhesion-modulating extracellular matrix molecule that is highly expressed in tumor stroma and stimulates tumor cell proliferation. Adhesion of T98G glioblastoma cells to a fibronectin substratum is inhibited by tenascin-C. To address the mechanism of action, we performed a RNA expression analysis of T89G cells grown in the presence or absence of tenascin-C and found that tenascin-C down-regulates tropomyosin-1. Upon overexpression of tropomyosin-1, cell spreading on a fibronectin/tenascin-C substratum was restored, indicating that tenascin-C destabilizes actin stress fibers through down-regulation of tropomyosin-1. Tenascin-C also increased the expression of the endothelin receptor type A and stimulated the corresponding mitogen-activated protein kinase signaling pathway, which triggers extracellular signal-regulated kinase 1/2 phosphorylation and c-Fos expression. Tenascin-C additionally caused down-regulation of the Wnt inhibitor Dickkopf 1. In consequence, Wnt signaling was enhanced through stabilization of beta-catenin and stimulated the expression of the beta-catenin target Id2. Finally, our in vivo data derived from astrocytoma tissue arrays link increased tenascin-C and Id2 expression with high malignancy. Because increased endothelin and Wnt signaling, as well as reduced tropomyosin-1 expression, are closely linked to transformation and tumorigenesis, we suggest that tenascin-C specifically modulates these signaling pathways to enhance proliferation of glioma cells.

The implementation of the 'International Classification of Functioning, Disability and Health' (ICF) in daily practice of neurorehabilitation: an interdisciplinary project at the Kantonsspital of Lucerne, Switzerland

PURPOSE

The current paper describes the implementation of ICF as a standard language and framework for description of human functioning and disability for common use in every day work by the multiprofessional team.

METHOD

An interdisciplinary project team involving all rehabilitation specialities was constituted. The extensive original document of ICF was broken down to a simplified raster for body functions and structures, activities and participation, as well as for contextual factors. These rasters had to cover the most important aspects concerning the patients treated on our unit. Checklists on the basis of these rasters were worked out for use by the different specialized teams. Using these checklists, rehabilitation conferences, form and language of interdisciplinary communication, goal setting and documentation were introduced newly in every day work for the interdisciplinary rehabilitation team, structured strictly based on the ICF-criteria.

RESULTS

Since April 2002 the ICF-based processes are implemented in routine work for all members of the rehabilitation staff. First experiences show good acceptance by the team members, improvements in communication and documentation as well as substantial gains in content and handling of rehabilitation conferences. As a result of the implementation we observed, that participation, context and domiciliary interventions gained quite more influence in every day work at the unit.

CONCLUSION

Implementation improved considerably the quality of interdisciplinary work processes and contributed to a more systematic approach to rehabilitation tasks by the team members.

[Obstructive urolithiasis in a female lamb]

In this report, the case of a 2-month-aged female lamb with obstructive urolithiasis, caused by calculi consisting of calcium-phosphate (apatite), is described. Urolithiasis as an often occurring problem in male sheep rarely emerges in female individuals. This lies mainly on the differences in anatomy between male and female urogenital apparatus. The account of diagnosis, therapy and clinical course in that special case are discussed, along with possible causes of the disease, the etiopathogenesis and recommended prophylactic steps.

Ultrasonographic findings in five cows before and after treatment of reticular abscesses

Five cows with reticular abscesses were examined clinically, haematologically, radiographically and ultrasonographically. They all had clinical signs typical of traumatic reticuloperitonitis, including chronic indigestion, pyrexia, an absence of or reduced ruminal motility, weight loss and a positive reaction to foreign body test. A haematological examination revealed anaemia, increased concentrations of plasma protein and fibrinogen and a decreased clotting time in the glutaraldehyde test. On the basis of the radiographic examination, a tentative diagnosis of reticular abscess was made in four of the cows, because the reticulum was displaced from the peritoneum or because there was an extensive gas-fluid interface in the reticular region. By ultrasonography, a large reticular abscess with a well developed capsule was visible in each of the cows. The abscess was located between the reticulum and ventral peritoneum in two of them, between the reticulumn and right thoracic wall in two and between the reticulum and spleen in the other cow. A foreign body penetrating the abscess could be visualised ultrasonographically in one cow. In two cows, the abscesses were drained through an ultrasound-guided transcutaneous incision. In the other three cows, the abscess was incised and drained from within the reticulum during a rumenotomy. Ultrasonographic examination revealed that the abscess had been completely evacuated in four cows, but only by about two-thirds in the remaining cow. All the cows were clinically healthy when they were discharged.

Stabilisation of a mandibular fracture in a cow by means of a pinless external fixator

A four months pregnant, four-year-old Brown Swiss cow with mandibular fractures of the right horizontal ramus and the symphysis was treated surgically with a new pinless external fixator. Healing was complicated by the sequestration of bone at the fracture site. After the sequestrum had been removed a radiographic examination revealed that the fracture had healed completely.

Pinless external fixation of mandible fractures in cattle

OBJECTIVE

This report describes our experience with a new technique for stabilization of mandibular fractures in cattle using a pinless external fixator.

STUDY DESIGN

Mandibular fractures were stabilized with a pinless external fixator, which is a modification of a unilateral AO/ASIF (Association for the Study of Internal Fixation)-fixator in which pins are replaced with bone clamps.

ANIMALS

Seven dairy cattle between 1 and 5 years of age.

METHODS

Fracture stabilization was achieved by using the pinless external fixator. Postoperative management included intravenous administration of sodium chloride-glucose and antibiotics. A suspension of ruminal contents from a normal cow together with linseed and grass pellets was administered with a gastric tube.

RESULTS

Three to 10 days after surgery six of seven cows masticated comfortably. The only failure was a yearling with a 10-day-old open infected fracture. This animal was slaughtered 9 days after surgery because of additional problems. In six cases there was enough callus formation 33 to 54 days after surgery to stabilize the fracture. The fixation devices were removed under heavy sedation. The major complication was bone sequestration at the fracture site, which required additional treatment.

CONCLUSION

The pinless fixator has proven satisfactory for external stabilization of unilateral horizontal ramus fractures of the mandible in cattle.

CLINICAL RELEVANCE

The technique provides good stability without penetration of the medullary cavity and damage to the tooth roots. Other advantages of the technique include ease of application, minimal surgical trauma, and the short surgical time for application.

Toxocara canis: a labile antigenic surface coat overlying the epicuticle of infective larvae

An electron-dense coat covering the surface of Toxocara canis infective-stage larvae is described. This coat readily binds to cationized ferritin and ruthenium red, indicating a net negative charge and mucopolysaccharide content, and can be visualized by immuno-electron microscopy only if cryosectioning is employed. Monoclonal antibodies reactive to the surface of live larvae bind the surface coat but not the underlying cuticle in ultrathin cryosections. The surface coat is dissipated on exposure to ethanol, explaining the lack of surface reactivity of conventionally prepared immunoelectron microscopy sections of T. canis. Differential ethanol extraction of surface-iodinated larvae demonstrates that the major component associated with the coat is TES-120, a 120-kDa glycoprotein previously identified by surface iodination, which is also a dominant secreted product. The surface-labeled TES-70 glycoprotein is linked with a more hydrophobic stratum at the surface, while a prominent 32-kDa glycoprotein, TES-32, is more strongly represented within the cuticle itself. Antibody binding to the coat under physiological conditions results in the loss of the surface coat, but this process is arrested at 4 degrees C. This result gives a physical basis to earlier observations on the shedding of surface-bound antibodies by this parasite. An extracuticular surface coat has been demonstrated on Toxocara larvae prior to hatching from the egg and during all stages of in vitro culture, suggesting that it may play a role both in protecting the parasite on hatching in the gastrointestinal tract and on subsequent tissue invasion in evading host immune responses directed at surface antigens.